The clinician's expectations from the use of positron emission tomography/computed tomography scanning in untreated and treated head and neck cancer patients

PET/MR in cancers of the head and neck

One early application of PET/MRI in clinical practice may be the imaging of head and neck cancers. This is because the morphologic imaging modalities, CT and MR, are recognized as similarly effective tools in cross-sectional oncological imaging of the head and neck. The addition of PET with FDG is believed to enhance the accuracy of both modalities to a similar degree. However, there are a few specific scenarios in head and neck cancer imaging where MR is thought to provide an edge over CT, including perineural spread of tumors and the infiltration of important anatomical landmarks, such as the prevertebral fascia and great vessel walls. Here, hybrid PET/MR might provide higher diagnostic certainty than PET/CT or a separate acquisition of PET/CT and MR. Another advantage of MR is the availability of several functional techniques. Although some of them might enhance the imaging of head and neck cancer with PET/MR, other functional techniques actually might prove dispensable in the presence of PET. In this overview, we discuss current trends and potential clinical applications of PET/MR in the imaging of head and neck cancers, including clinical protocols. We also discuss potential benefits of implementing functional MR techniques into hybrid PET/MRI of head and neck cancers.

A case of primary lung cancer lesion demonstrated by F-18 FDG positron emission tomography/computed tomography (PET/CT) one year after the detection of metastatic brain tumor

Cancer of unknown primary origin (CUP) is an aggressive disease with a poor prognosis. Metastatic brain tumors occur in approximately 15% of all cancer patients. F-18 2'-deoxy-2fluoro-D-glucose (FDG) positron emission tomography (PET) combined with computed tomography (PET/CT) contributes to the evaluation of cancer staging, although the benefits of PET/CT for detection of CUP origins has yet to be determined. In this study, we present a 37-year-old man with a brain tumor detected by magnetic resonance imaging. Surgical biopsy indicated a metastatic undifferentiated carcinoma, while clinical examination and a CT scan did not detect any abnormalities, with the exception of brain metastases. PET/CT did not reveal abnormal FDG uptake. PET/CT revealed abnormal intense FDG uptake in a small nodular lesion in the right lung 1 year following the detection of brain metastasis, and no other abnormal FDG uptake was observed elsewhere in the body. Right upper lobectomy and dissection of mediastinal lymph nodes were performed. The pathological diagnosis was poorly differentiated adenocarcinoma, which was similar to the brain metastatic lesion, and there was no lymph node metastasis. This case revealed an extremely rare lung cancer with primary lesions demonstrated by PET/CT 1 year after the detection of brain metastasis. This case reveals that F-18 FDG PET/CT imaging of CUP origin is capable of positively impacting on the identification of small primary tumor foci.

A case of early stage lung cancer detected by repeated cancer screening with positron emission tomography

There has been an increase in the detection rate of small early lung cancer due to recent improvements in imaging technology. However, conventional imaging modalities such as computed tomography (CT) alone are not capable of differentiating small pulmonary nodules. New modalities such as F-18 2'-deoxy-2fluoro-D-glucose (FDG) positron emission tomography combined with CT (PET/CT) have contributed to the evaluation of lung cancer staging, although the differential diagnosis of pulmonary nodules showing ground-glass opacity (GGO) with PET/CT is controversial. In Japan, cancer screening with whole body FDG-PET has been available for asymptomatic individuals, and it has been reported that a wide variety of cancer types are detectable by FDG-PET at potentially curable stages. We present the case of a 62-year-old male with early lung cancer, which was revealed by repeated health screening. A PET/CT scan revealed definite intense FDG uptake (SUVmax 1.2) in the pulmonary nodules of the right upper lobe, while no definite FDG uptake was observed in the lesion in the previous annual screening. Right upper lobectomy was performed, and the pathological diagnosis was well-differentiated adenocarcinoma. Five-year survival has been noted since the thoracotomy, and the patient is doing well without recurrence. This is a significant case of early lung cancer with GGO lesions, which revealed intense FDG uptake during an annual repeated health screening with FDG-PET/CT.

Diagnostic Value of Only 18F-fluorodeocyglucose Positron Emission Tomography/Computed Tomography–Positive Lymph Nodes in Head and Neck Squamous Cell Carcinoma

Objective

The role of 18F-fluorodeocyglucose positron emission tomography (PET)/computed tomography (CT) in only PET/CT–positive lymph nodes (LNs) is not well elucidated yet. This study was conducted to evaluate the diagnostic value of only PET/CT–positive LNs without correlating positive findings on conventional imaging modalities (CT, magnetic resonance imaging [MRI], and ultrasound [US]) in patients with head and neck squamous cell carcinoma (HNSCC).

Study Design

Case series with chart review.

Setting

Hallym University School of Medicine.

Subjects and Methods

From January 2006 to September 2009, 114 patients with HNSCC who underwent CT, MRI, US, and PET/CT before definitive surgery with neck dissection were reviewed. All imaging tests were interpreted on imaging-based nodal classification and were compared with histopathological findings.

Results

Only PET/CT–positive LNs were found at 48 nodal levels in 33 patients. Thirteen of 48 (27%) nodal levels were true-positive (TP), and 35 of 48 (73%) were false-positive (FP). Fourteen nodal levels were included on N+ necks, and 34 were included on N0 necks. In N0 necks, the FP rate was significantly higher than the TP rate (28 vs 6, P = .034). Eleven only PET/CT–positive nodal levels in 10 patients were found on the contralateral neck side, and FP was significantly more prevalent than TP (8 vs 3, P = .041). No significant difference was observed for mean standardized uptake value and LN sizes between TP and FP.

Conclusion

Only PET/CT–positive LNs can frequently be found and do not predict LN metastasis, because a high percentage of results were FP. Our results suggest that only PET/CT–positive LNs should be considered negative, especially in N0 and contralateral necks.

18F-FDG PET/CT imaging in oncology

Accurate diagnosis and staging are essential for the optimal management of cancer patients. Positron emission tomography with 2-deoxy-2-[fluorine-18]fluoro-D-glucose integrated with computed tomography (18F-FDG PET/CT) has emerged as a powerful imaging tool for the detection of various cancers. The combined acquisition of PET and CT has synergistic advantages over PET or CT alone and minimizes their individual limitations. It is a valuable tool for staging and restaging of some tumors and has an important role in the detection of recurrence in asymptomatic patients with rising tumor marker levels and patients with negative or equivocal findings on conventional imaging techniques. It also allows for monitoring response to therapy and permitting timely modification of therapeutic regimens. In about 27% of the patients, the course of management is changed. This review provides guidance for oncologists/radiotherapists and clinical and surgical specialists on the use of 18F-FDG PET/CT in oncology.